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| Titel |
Atmospheric patterns for wildfires caused by lightning in Castile and León, Spain |
| VerfasserIn |
E. García-Ortega, M. T. Trobajo, L. López |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025565
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| Zusammenfassung |
| Castile and León, Spain, is the third largest region in Europe, with 94225Â km2, and has a
forest area of nearly 50000Â km2. Every year an average of 1,800 wildfires scorch forests in
this region and 8% of these fires are ignited by lightning during thunderstorms. Lightning
plays an important role in devastating fires that burn large areas. Critical fire-weather
conditions are the prime ingredients needed to fuel a fire that may rage for long periods of
time. The land area affected by this type of fire is generally larger than in the case of fires
with a different origin because storms often bring with them strong and erratic
winds making the extinction of the fire more difficult. Most summer storms occur
in mountainous regions and during the night, thus contributing to larger affected
areas.
The Group for Atmospheric Physics (GAP) at the University of León (ULE), Spain, is
currently engaged in a research Project cooperating with the Center for the Defense
against Fire (CDF) of the Regional Government in Castile and León. The final
aim is to develop a forecast model for fire risk based on the identification of the
meteorological situations that may lead to convective phenomena including storms with
lightning.
The project has several stages. Firstly, we focus on identifying the patterns of
the synoptic and mesoscale atmospheric circulation in the affected areas during
wildfire days caused by lightning, from 1985 to 2006. The database contains 376 days
that caused 973 wildfires, with affected land areas between 1 and 5000 hectares.
Gridded data from the National Centers for Environmental Prediction (NCEP), with a
2.5o à 2.5o latitude-longitude resolution, are used. The study area comprises the
domain from 30o N to 60o N and from 30o W to 10o E. The selection of a group of
independent variables representative of the state of the atmosphere will supply
-by means of a clustering procedure- a synoptic and mesoscale meteorological
categorization of the atmospheric characteristics of these days. The Principal Component
Analysis (PCA) will be applied previously to extract the most important components of
the initial variables and to explore the joint space and time variations in the data
set.
In this preliminary study, a subjective classification of the atmospheric patterns has been
carried out corresponding to the fire days in the province of León (15500Â km2), the one most
severely affected in Castile and León, with 326 fires in 161 days. The variables used have
been sea level pressure and 500-hPa geopotential height. An additional objective
classification was carried out. Using the time steps as variables and the grid points as
observations, we have used the PCA (in T-mode) to isolate groups of time steps with similar
patterns. The results obtained enable us to describe the characteristics of the various synoptic
environments. However, it seems obvious that a forecast model based on the results of cluster
analysis classification requires a more complete set of independent variables obtained
from a group of fields, such as geopotential height, relative humidity or horizontal
component of wind. This classification will be the next stage in the present research
Project. |
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